Respiratory Organs & Human System — NEET Biology MCQs with Solutions
Free NEET Biology Respiratory Organs & Human System MCQs with step-by-step solutions (58 questions). Part of Breathing and Exchange of Gases. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Respiratory Organs & Human System · easy · theory
The functional units of the lung where gas exchange occurs are the:
A. Alveoli ✓ Correct
B. Bronchi
C. Trachea
D. Larynx
Solution: Alveoli are thin-walled, vascularised sacs where diffusion of O₂ and CO₂ takes place.
Q2 — Respiratory Organs & Human System · easy · theory
The organ commonly called the voice box, located at the beginning of the trachea, is the:
A. Epiglottis
B. Pharynx
C. Bronchus
D. Larynx ✓ Correct
Solution: The larynx (voice box) helps in sound production; the epiglottis covers it during swallowing.
Q3 — Respiratory Organs & Human System · medium · theory
Which structure prevents food from entering the trachea (windpipe) during swallowing?
A. Glottis
B. Epiglottis ✓ Correct
C. Diaphragm
D. Pleura
Solution: The epiglottis is a cartilaginous flap that covers the glottis during swallowing, directing food to the oesophagus.
Q4 — Respiratory Organs & Human System · medium · theory
The part of the respiratory pathway that only conducts air (no gas exchange) includes all EXCEPT:
A. Alveoli ✓ Correct
B. Trachea
C. Bronchioles
D. Bronchi
Solution: The conducting zone (nostrils to terminal bronchioles) transports/cleans/moistens air; exchange occurs only in the alveoli.
Q5 — Respiratory Organs & Human System · hard · theory
The double-membrane pleura around the lungs, with pleural fluid between its layers, functions to:
A. Exchange gases
B. Reduce friction and allow smooth lung movement during breathing ✓ Correct
C. Store air
D. Produce mucus for digestion
Solution: Pleural fluid lubricates the lung surface, minimising friction against the thoracic wall during breathing.
Q6 — Respiratory Organs & Human System · hard · theory
Which sequence correctly traces air from outside to the site of gas exchange?
A. Trachea → bronchi → pharynx → alveoli
B. Nostrils → pharynx → larynx → trachea → bronchi → bronchioles → alveoli ✓ Correct
C. Nostrils → larynx → pharynx → bronchi → alveoli → trachea
D. Nostrils → trachea → pharynx → alveoli
Solution: Air passes: external nostrils → nasal chamber → pharynx → larynx → trachea → primary bronchi → bronchioles → alveoli.
Q7 — Respiratory Organs & Human System · easy · numerical
In which group of animals is a branching network of air-filled tracheal tubes the chief respiratory structure that carries air directly to the body tissues?
A. Amphibians
B. Bony fishes
C. Insects ✓ Correct
D. Mammals
Solution: Insects have a tracheal system that delivers air (and O₂) directly to tissues through tracheoles, so they do not depend on blood for O₂ transport.
Q8 — Respiratory Organs & Human System · easy · numerical
A frog can supplement its pulmonary breathing by exchanging gases across its:
A. gills
B. moist, vascular skin ✓ Correct
C. tracheae
D. air sacs
Solution: In amphibians such as frogs the thin, moist and richly vascularised skin permits cutaneous respiration in addition to lung breathing.
Q9 — Respiratory Organs & Human System · easy · numerical
The human trachea is prevented from collapsing during breathing by:
A. complete rings of bone
B. closely packed alveoli
C. incomplete, C-shaped cartilaginous rings in its wall ✓ Correct
D. a thick layer of smooth muscle only
Solution: The trachea is supported by incomplete (C-shaped) cartilaginous rings that keep the airway open while allowing the oesophagus behind it to expand.
Q10 — Respiratory Organs & Human System · easy · numerical
Fishes carry out exchange of gases with the surrounding water mainly through their:
A. moist skin
B. lungs
C. gills ✓ Correct
D. tracheae
Solution: Aquatic animals like fishes use gills, whose vascularised filaments extract dissolved oxygen from water.
Q11 — Respiratory Organs & Human System · medium · numerical
Match the animal with its principal respiratory structure: (i) Earthworm (ii) Cockroach (iii) Fish (iv) Frog — with (p) gills (q) moist skin and lungs (r) moist body surface (s) tracheal tubes.
A. i-r, ii-s, iii-q, iv-p
B. i-q, ii-s, iii-p, iv-r
C. i-s, ii-r, iii-p, iv-q
D. i-r, ii-s, iii-p, iv-q ✓ Correct
Solution: Earthworm uses its moist body surface, cockroach (insect) uses tracheae, fish uses gills, and frog uses moist skin along with lungs.
Q12 — Respiratory Organs & Human System · medium · numerical
Assertion (A): The bronchioles can narrow markedly during an asthmatic attack. Reason (R): Bronchioles lack supporting cartilage and have smooth muscle in their walls.
A. A is true but R is false
B. A is false but R is true
C. Both A and R are true but R is not the correct explanation of A
D. Both A and R are true and R is the correct explanation of A ✓ Correct
Solution: Unlike the trachea and bronchi, bronchioles have no cartilage; their smooth-muscle walls can contract, so they narrow during bronchospasm as in asthma.
Q13 — Respiratory Organs & Human System · medium · numerical
Which of the following is a role of the conducting part of the respiratory system?
A. It carries out the actual diffusion of O₂ and CO₂
B. It forms the site where oxyhaemoglobin is produced
C. It secretes surfactant that oxygenates the blood
D. It warms, moistens and filters the incoming air before delivering it to the exchange region ✓ Correct
Solution: The conducting part (nostrils to terminal bronchioles) transports, cleans, humidifies and warms the air; gas exchange itself occurs only in the respiratory part (alveoli).
Q14 — Respiratory Organs & Human System · medium · numerical
The pleural membrane in direct contact with the lung surface is the ______ pleura, whereas the one lining the inner thoracic wall is the ______ pleura.
A. parietal; visceral
B. serous; mucous
C. visceral; parietal ✓ Correct
D. costal; diaphragmatic
Solution: The inner (visceral) pleura covers the lungs and the outer (parietal) pleura lines the thoracic wall, with pleural fluid between them.
Q15 — Respiratory Organs & Human System · medium · numerical
The extremely large surface area available for gas exchange in the human lungs is provided by roughly 300 million alveoli, giving a total area of about:
A. 1 m²
B. 1000 m²
C. 10 m²
D. 100 m² ✓ Correct
Solution: The alveoli together provide an enormous diffusion surface of about 100 m², enabling efficient gas exchange in a compact volume.
Q16 — Respiratory Organs & Human System · medium · numerical
Which of the following statements about the human respiratory system is INCORRECT?
A. Exchange of gases takes place across the walls of the trachea and primary bronchi ✓ Correct
B. Air is filtered, warmed and moistened as it passes through the conducting part
C. The alveoli are the primary sites of exchange of gases
D. The nasal chamber, pharynx, larynx, trachea and bronchi form the conducting part
Solution: No gas exchange occurs in the trachea or bronchi (conducting part); diffusion of O₂ and CO₂ takes place only across the alveolar walls.
Q17 — Respiratory Organs & Human System · easy
In which of the following does gaseous exchange between O2 and CO2 occur through the general body surface?
A. Sponges
B. Coelenterates
C. Flatworms
D. All ✓ Correct
Solution: Sponges, coelenterates and flatworms all exchange gases by simple diffusion across their general body surface.
Q18 — Respiratory Organs & Human System · medium
Match the animals in Column I with their respiratory organs in Column II and select the correct option.
A. Earthworms
B. Most aquatic arthropods
C. Fishes
D. Birds/Reptiles
E. Insects
1. Lungs
2. Trachea
3. Gills
4. Moist cuticle
A. A-IV, B and C-III, D-I, E-II ✓ Correct
B. A-IV, B-III, C and D-I, E-III
C. A-II, B and C-III, D-I, E-IV
D. A-III, B and C-I, D-II, E-IV
Solution: Earthworm uses moist cuticle, aquatic arthropods and fishes use gills, birds/reptiles use lungs, and insects use tracheae.
Q19 — Respiratory Organs & Human System · easy
Amphibians, e.g. frogs, respire through
A. Trachea
B. Lungs
C. Both (1) and (2) ✓ Correct
D. Through moist skin
Solution: Frogs respire through their moist skin (cutaneous) as well as through their lungs.
Q20 — Respiratory Organs & Human System · medium
Which is the correct sequence of air passages in man?
A. Nose → Larynx → Bronchi → Pharynx → Trachea → Bronchioles → Alveoli
B. External nostril → Nasal passage → Internal nostril → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli ✓ Correct
C. Nose → Pharynx → Trachea → Larynx → Bronchi → Bronchioles → Alveoli
D. Nose → Larynx → Pharynx → Bronchioles → Bronchi → Alveoli
Solution: Air flows: external nostril → nasal passage → internal nostril → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.
Q21 — Respiratory Organs & Human System · medium
Which is correct about the nasopharynx?
A. All ✓ Correct
B. Internal nostrils open into nasopharynx
C. It is the common passage for both air and food
D. It opens through the gullet of the larynx region into the trachea
Solution: The nasopharynx receives the internal nostrils, serves as a common air-food passage, and leads through the larynx into the trachea.
Q22 — Respiratory Organs & Human System · easy
Which of the following options is wrong about the larynx (sound box)?
A. It is a bony box ✓ Correct
B. All
C. Glottis is the opening into the larynx
D. During swallowing of food glottis is covered by epiglottis to prevent food entry into the larynx
Solution: The larynx is a cartilaginous box, not a bony box, so that statement is wrong.
Q23 — Respiratory Organs & Human System · easy
Trachea divides into right and left primary bronchi at the ______ thoracic vertebra.
A. 9
B. 6
C. 4
D. 5 ✓ Correct
Solution: The trachea divides into the two primary bronchi at the level of the 5th thoracic vertebra.
Q24 — Respiratory Organs & Human System · medium
Incomplete cartilaginous rings support all of the following except
A. Initial bronchioles
B. Primary, secondary and tertiary bronchi
C. Respiratory bronchioles ✓ Correct
D. Trachea
Solution: Incomplete cartilaginous rings support the trachea, bronchi and initial bronchioles but not the respiratory bronchioles.
Q25 — Respiratory Organs & Human System · easy
Which of the following has the smallest diameter?
A. Terminal bronchiole ✓ Correct
B. Trachea
C. Tertiary bronchus
D. Secondary bronchus
Solution: Among these, the terminal bronchiole has the smallest diameter as airways progressively narrow.
Q26 — Respiratory Organs & Human System · easy
Lungs are comprised of
A. Only alveoli
B. Different types of bronchi
C. Network of bronchi, bronchioles and alveoli ✓ Correct
D. Pleura
Solution: Each lung is a network of bronchi, bronchioles and alveoli.
Q27 — Respiratory Organs & Human System · easy
Sites of gaseous exchange in the lungs are
A. Tracheoles
B. Pleura
C. Bronchioles
D. Alveoli ✓ Correct
Solution: The alveoli are the thin-walled vascularised sites of gas exchange in the lungs.
Q28 — Respiratory Organs & Human System · medium
Consider the following features:
I. It is double layered and covers the lungs.
II. Fluid between the layers reduces friction on the lung-surface.
III. Outer layer is in contact with the thoracic wall.
IV. Inner layer is in contact with the lungs.
The above features refer to
A. None
B. Pleura ✓ Correct
C. Pericardium
D. Peritoneum
Solution: The pleura is a double-layered membrane whose fluid reduces friction; the parietal layer contacts the thoracic wall and the visceral layer contacts the lungs.
Q29 — Respiratory Organs & Human System · easy
The part starting with the external nostrils up to the terminal bronchioles constitutes the
A. Inspiratory part
B. Conducting part ✓ Correct
C. Expiratory part
D. Respiratory or exchange part of respiratory system
Solution: From the external nostrils to the terminal bronchioles forms the conducting part of the respiratory system.
Q30 — Respiratory Organs & Human System · medium
The respiratory or exchange part of the respiratory system consists of
A. All bronchi and terminal bronchioles
B. All bronchioles
C. The parts starting with external nostrils up to terminal bronchioles
D. Alveoli and their ducts ✓ Correct
Solution: The exchange part comprises the alveoli and their ducts, where gas exchange occurs.